1. Field of the Invention
The subject invention relates generally to pumps and, more particularly, to a method and apparatus for microscopic scale pumping of a fluid employing a micromachined electrostatic pumping device.
2. Description of Related Art
As reported in the article "Peristaltic Pumping" by M. Y. Jaffrin and A. H. Shapiro (1971), peristaltic pumping is a form of fluid transport that occurs when a progressive wave of area contraction or expansion propagates along the length of a distensible tube containing a liquid. Physiologically, peristaltic action is an inherent neuromuscular property of any tubular smooth muscle structure. This characteristic is put to use by the body to propel or to mix the contents of a tube, as in the ureters, the gastrointestinal tract, the bile duct, and other glandular ducts.
Peristalsis is also the mechanism by which roller or finger pumps operate. Here the tube is passive, but is compressed by rotating rollers, by a series of mechanical fingers, or by a nutating plate. These devices are used to pump blood, slurries, corrosive fluids, and foods, whenever it is desirable to prevent the transported fluid from coming into contact with the mechanical parts of the pump. Generally the compression mechanism occludes the tube completely or almost completely, and the pump, by positive displacement, "milks" the fluid through the tube.
While the prior art has addressed various small electrostatic or piezo-driven pumps, no truly microperistaltic-type pump has been provided. Prior art proposals include devices employing triple chambers with valving, typically implemented with piezo devices. Such systems are not truly peristaltic.